Hitherto, a wet system of reproducing images by wet processing after photographing or recording on silver halide photographic light-sensitive materials has been adopted in an apparatus for recording images for medical use, e.g., CT (computer tomography), MRI (magnetic resonance imaging) or the like.
As opposed to such a wet system, a recording apparatus adopting a dry system free from wet processing has received much attention in recent years. In such an apparatus, for instance, films of a recording material sensitive to both light and heat (a light- and heat-sensitive recording material) or a heat-developable photosensitive material (these films are referred to as "recording films" hereinafter) have been used.
In such an apparatus for recording on heat-developable photosensitive materials, the recording films are irradiated with (exposed to) laser beams to form latent images therein, and then heated to produce or develop colors. The exposure operation therein is generally carried out by scanning laser beams (main scan) while controlling the output of laser beams in accordance with image data. Synchronously with the main scan, it is proper that the recording film under exposure be moved in the prescribed direction (side scan). And the development or the color production is generally effected by passing the exposed recording films through a heating device.
Additionally, the literature on such an apparatus for recording on heat-developable photosensitive materials includes, e.g., WO 95/31754, WO 95/30934 and so on.
Each time the photographing on a recording film is carried out, the size of the film used is properly chosen depending on the object of photographing (e.g., what part of the body is to be photographed) and so on. Therefore, the recording films fed into the heat development section are sometimes different in size.
As mentioned above, the development is performed by passing each recording film through a heating device. In a case where the heating device uses a heating drum, the temperature of the drum surface becomes lower in the region used for development (the region in which the drum surface is actually in contact with a recording film is hereinafter referred to as "the development region") than in the other region.
If the region used for development is always the same on the heating drum surface, the temperature of the development region is in a semi-stationary state even when plural sheets of recording film are developed continuously; as a result, steady development can be performed. However, in the case of changing the size of a recording film to be exposed, the location, area and shape of the development region become different from-what they are before the size change. As a result, the temperature distribution in the new development region lacks uniformity just after the size change to tend to cause development streaks.
In particular, this problem is serious when the recording film size is changed from small to large. As the recorded images are required to have high quality in the medical filed, recording films of high quality are used therein. However, the recording films capable of producing images of high quality are liable to be influenced by the temperature during heat development, and so they are in a condition to readily generate the foregoing development streaks.